Editing Local anesthetic (section)

==== Central nervous system ====

Depending on local tissue concentrations of local anesthetics, excitatory or depressant effects on the central nervous system may occur.

Initial symptoms of systemic toxicity include ringing in the ears ([[tinnitus]]), a metallic taste in the mouth, tingling or numbness of the mouth, dizziness and/or disorientation.

At higher concentrations, a relatively selective depression of inhibitory neurons results in cerebral excitation, which may lead to more advanced symptoms include motor twitching in the periphery followed by [[Grand Mal seizures|grand mal seizures]]. It is reported that seizures are more likely to occur when bupivacaine is used, particularly in combination with chloroprocaine.<ref name=":2">{{Cite book|url=https://books.google.com/books?id=NYiQYoPjJl4C&q=local+anesthesia+general+side+effects |title=Meyler's Side Effects of Drugs Used in Anesthesia| vauthors = Aronson JK |date=2008-10-07|publisher=Elsevier|isbn=9780444532701|language=en}}</ref>

A profound depression of brain functions may occur at even higher concentrations which may lead to [[coma]], [[respiratory arrest]], and death.<ref name="Mulroy, M. 2002">{{cite journal | vauthors = Mulroy MF | title = Systemic toxicity and cardiotoxicity from local anesthetics: incidence and preventive measures | journal = Regional Anesthesia and Pain Medicine | volume = 27 | issue = 6 | pages = 556–561 | date = 2002 | pmid = 12430104 | doi = 10.1053/rapm.2002.37127 | s2cid = 36915462 }}</ref> Such tissue concentrations may be due to very high plasma levels after intravenous injection of a large dose.

Another possibility is direct exposure of the central nervous system through the [[cerebrospinal fluid]], i.e., overdose in spinal anesthesia or accidental injection into the subarachnoid space in epidural anesthesia.